1. Field of the Invention
The present invention relates to tunnel boring machines of the type which move progressively through a tunnel while boring the same. Such machines are of necessity quite large and the space available in a tunnel is limited. Thus there is in this field a continual search for new ways to conserve space in the tunnel by efficient arrangement of the parts of the tunnel boring machine.
Another goal is to achieve versatility, i.e. to allow various parts of the tunnel boring machine as well as other equipment to be located in any one of a number of possible places in accord with the needs of a particular drilling job. This in turn allows the workers to move more freely about the tunnel space and to perform their tasks more easily.
2. Brief Descriptionn of the Prior Art
One of the most popular types of tunnel boring machines has been the type shown in U.S. Pat. No. 3,598,445. This type of machine generally comprises a rotary cutterhead assembly, with cutting means on its forward face, rotatably mounted on a cutterhead support assembly. The axis of rotation is generally coincident with the longitudinal centerline of the tunnel. A main beam extends from the cutterhead support assembly along this axis, and a gripper assembly is slidably mounted thereon. Hydraulic drive cylinders interconnecting the gripper assembly and the cutterhead support assembly serve to drive the cutterhead and cutterhead support forward against the end face of the tunnel when the grippers of the gripper assembly are engaging the tunnel wall. They are also operative to pull the gripper assembly forward on the main beam when its grippers are disengaged.
In such machines it is necessary to provide some means for transmitting torque from the cutterhead support assembly to the gripper assembly, via the main beam, during drilling. This is particularly true of those machines in which the cutterhead support assembly is mounted on the forward end of the main beam by means of a ball joint or other type of universal joint. One common way of doing this is to provide a special set of hydraulic torque reaction cylinders interconnecting the cutterhead support assembly and the main beam. In some cases, where the cutterhead support assembly is mounted on a universal joint, the cylinders used to control vertical and horizontal attitude of the cutterhead support assembly relative to the main beam may also be used to transmit the torque.
In order to conserve space in such a machine, the conveyor used to carry cuttings to the rear of the machine is disposed within the main beam. The relative positions of the parts of the machine, as described above, are dictated by the nature of the machine and particularly by the main beam. There is little versatility in such a structure. Furthermore, the main beam, located in the center of the tunnel, occupies the most valuable space and divides the remaining space so that no large open area is available in the vicinity of the machine.